Formation and stability of charged amino acid clusters and the role of chirality

Abstract

Amino acid clusters have been studied by several groups and most notably magic number clusters and chiral recognition have been reported. In this work, we have studied the formation of amino acid clusters by electrospray ionization (ESI) and their stability by high-energy collision-induced dissociation (CID). Appearance sizes were determined for multiply charged clusters where the charge is either due to protons or to sodium ions. Finally, we conclude that chiral selectivity plays an important role in cluster formation but seems to be of minor importance for the fragmentation of mixed clusters.

Standard-Free Quantitation of Mixtures Using Clusters Formed by Electrospray Mass Spectrometry

“…The weighting of these data either by their respective abundances or cluster sizes results in a negligible change in the percent molar fraction determined. The molar fraction of L-threonine determined just from octameric clusters is 1.6% ± 0.5%, indicating that the octamer can readily incorporate L-threonine as previously reported 43, 45, 53…”

Formation of [nM−nH+(n+1)Na]+ cluster ions from amino acid by electrospray ionization

“…The [nM−nH+(n + 1)Na] + ions of amino acids have not been reported, but the [nM−nH+(n + 1)Na] + ions of peptides such as achatin-I [26] and phosphotyrosine peptide [27] were reported. Protonated cluster ions, [nM+H] + of amino acids generated by ESI were reported [21,22]. Concina and coworkers [22] also observed [nM+Na] + , [nM+H+Na] 2+ , and [nM+H+2Na] 3+ of serine.…”

“…Protonated cluster ions, [nM+H] + of amino acids generated by ESI were reported [21,22]. Concina and coworkers [22] also observed [nM+Na] + , [nM+H+Na] 2+ , and [nM+H+2Na] 3+ of serine. Cooks and coworkers reported sodiated serine clusters as well as protonated serine clusters using LC/ESI-MS and ion mobility-mass spectrometry [28,29].…”

“…Zhan and coworkers [15] reported re-solvation of bare electrospray-generated peptide ions in the lens region of the mass spectrometer that resulted from nucleation within the supersonic expansion jet. Analysis of amino acids using liquid chromatography/mass spectrometry (LC/MS) has been studied [16][17][18][19][20][21][22][23]. Some researchers [17,18] anaylzed underivatized amino acids for the diagnosis and therapy assessment.…”

“…Some researchers [17,18] anaylzed underivatized amino acids for the diagnosis and therapy assessment. Protonated cluster ions of amino acids, [nM+kH] k+ were reported [21,22] and Nanita and coworkers reported alkali metal-cationized serine clusters [23].…”